A lot of young men filled with love (5)
I believe the answer is:
loads
'a lot of' is the definition.
(I've seen this before)
'young men filled with love' is the wordplay.
'young men' becomes 'lads' (I've seen this in another clue).
'filled with' indicates putting letters inside.
'love' becomes 'o' (love means zero in tennis).
'lads' enclosing 'o' is 'LOADS'.
(Other definitions for loads that I've seen before include "Oodles (informal)" , "things to be carried" , "Washing jobs" , "A great many" , "Heavy weights to be carried" .)